1. verb+ it+ adj./noun (for/of) to do/clause (verb=think, believe, suppose, consider, feel, make, keep…)例I think it hard for you to do the task on your own./I think it hard that you'll do the task on your own.
2. verb+it+adj./noun (one's) doing (adj.=useless/worth/worthwhile)(noun=no use/no good/worth one's while/a waste of time/money/energy/words) (verb=think, believe, suppose, consider, feel, make, keep…)例I'll make it worth your while telling me about his secret.
3. verb+it+ important/unimportant/necessary/unnecessary/natural/essential that … (should)…verb+it+of much/great/no/little importance that…(should)…(verb=think, believe, suppose, consider, feel, make, keep…)例I think it important that you (should) attendthe conference.
4. verb + it+ as+ noun/adj.+ clause (verb=accept, regard, take, see, view)例The lecturer takes it as encouraging when so many students attend his lecture.
5. v. +it + prep. + that…owe it to sb. that…把…归功于…leave it to sb that…把…留给某人去做take it for granted that …想当然keep it in mind that…例Don't bother to arrange anything. Just leave it to me to sort out.
6. It用在不能直接跟宾语从句的动词后面，尤其是表示好恶的动词后，enjoy, like, love, dislike, resent, hate, don't mind, be fond of, feel like, see to 宾语从句紧跟it之后例I hate it you can swim so well and I can't.
7. It用在不能直接跟宾语从句的介词后面，宾语从句紧跟it之后（except that例外）例I'm for it that you will follow their advice.